I have been practicing C and so I thought making a file encryption and decryption program would be good practice.However as I was working on the problem of displaying the encrypted form of the files content on the terminal, I came across a challenge with displaying the characters I stored in the buffer on the terminal, The values displayed when I use the printf function seem to be incomplete and when I use a for loop to iterate through and print each character in the buffer, some characters end up being ignored. I have tried debugging but there has been close to no progress. I would really appreciate it if someone could let me know what went wrong.
#include <stdio.h>
#include <stdbool.h>
void encrypt(char* path );
void decrypt(char* );
int main(void){
char input;
printf("Hello, please enter the path of the file you want to encrypt\n");
char path[1024];
scanf("%s",path);
printf("File Path:%s\nFile encrypted content: ",path);
FILE *file = fopen(path, "r+");
if(file==NULL){
printf("Cannot open file \n");
system("pause");
return 1;
}
int ch;
int count = 0;
char buffer[1024];
while((ch=fgetc(file))!= EOF){
int hc = (ch + (count*2))%128;
printf("Original character: %c (ASCII value: %d) ", ch, ch);
buffer[count] = hc;
count++;
printf("Encrypted character: %c (ASCII value: %d)\n ", hc, hc);
if (count >= sizeof(buffer)-1){
printf("Buffer size exceeded");
break;
}
}
buffer[count] = '\0';
printf("This is the complete buffer\n\n");
for(int i=0; i<= count; i++){
printf("%c", buffer[i]);
}
printf("\nThis is the buffer printed as a string %s", buffer);
fclose(file);
system("pause");
return 0;
}
I initially run the program with a simple text file of about three words as input but when the encrypted characters were printed out, they were fewer than expected. I tried to print each character with its encrypted form as the encryption loop runs and the results were okay. All values stored in the buffer were successfully encrypted. But when I tried to print our the values in buffer using printf the problem still persisted. I tried using a for loop and it prints our almost all characters and some are left out.
Some of the characters in the encrypted data are null characters (characters with value zero). When your for loop encounters a null character, it prints it and continues. When the printf encounters a null character, it stops.
printf is designed this way because %s is for printing a C string, which is a string of characters whose end is marked by a null character. You cannot use printf with %s to print strings that contain internal null characters.
Additionally, directly printing characters in encrypted data is problematic because some characters are “non-printable” characters with special meanings, and they may not be preserved through the process of handling standard output, particularly when it is directed to a terminal. They should be written to a file in binary mode or converted for display (e.g., display their values in decimal or hexadecimal instead of printing them directly).